1. Field of the Invention
This invention relates to hard disk drives. More particularly, this invention relates to a suspension assembly having a stiffened vertically offset lift tab used in a rampload disk drive.
2. Description of the Prior Art and Related Information
A huge market exists for hard disk drives for mass-market host computer systems such as servers, desktop computers, and laptop computers. To be competitive in this market, a hard disk drive must be relatively inexpensive, and must accordingly embody a design that is adapted for low-cost mass production. In addition, it must provide substantial capacity, rapid access to data, and reliable performance. Numerous manufacturers compete in this huge market and collectively conduct substantial research and development, at great annual cost, to design and develop innovative hard disk drives to meet increasingly demanding customer requirements.
Each of numerous contemporary mass-market hard disk drive models provides relatively large capacity, often in excess of 2 gigabytes per drive. Nevertheless, there exists substantial competitive pressure to develop mass-market hard disk drives that have even higher capacities and that provide rapid access. Another requirement to be competitive in this market is that the hard disk drive must conform to a selected standard exterior size and shape often referred to as a "form factor." Generally, capacity is desirably increased without increasing the form factor or the form factor is reduced without decreasing capacity.
Satisfying these competing constraints of low-cost, small size, high capacity, and rapid access requires innovation in each of numerous components and methods of assembly including methods of assembly of various components into certain subassemblies. Typically, the main assemblies of a hard disk drive are a head disk assembly and a printed circuit board assembly.
The head disk assembly includes an enclosure including a base and a cover, at least one disk having at least one disk recording surface, a spindle motor for causing each disk to rotate, and an actuator arrangement. The printed circuit board assembly includes circuitry for processing signals and controlling operations.
Actuator arrangements can be characterized as either linear or rotary; substantially every contemporary cost-competitive small form factor drive employs a rotary actuator arrangement.
The rotary actuator arrangement is a collection of elements of the head disk assembly; the collection typically includes certain prefabricated subassemblies and certain components that are incorporated into the head disk assembly. The prefabricated assemblies include a pivot bearing cartridge and, in some cases, a prefabricated head stack assembly. Other components of the rotary actuator arrangement are permanent magnets and an arrangement for supporting the magnets to produce a magnetic field for a voice coil motor. The prefabricated head stack assembly includes a coil forming another part of the voice coil motor. The prefabricated head stack assembly also includes an actuator body having a bore through it, and a plurality of arms projecting parallel to each other and perpendicular to the axis of the bore. The prefabricated head stack assembly also includes head gimbal assemblies that are supported by the arms. Each head gimbal assembly includes a suspension assembly and a head supported by the suspension assembly.
Hard disk drives which are targeted for the desktop and server markets typically use a technique known as "Contact Start/Stop" ("CSS") to transition a "flying head" off-of and back-onto a surface of a magnetic disk. Typically, an annular region on the disk known as a "landing zone" is used to transition the head off-of and back-onto the surface of the disk. During a disk spin-down period, the head is moved to the landing zone and as the disk rotation speed decreases, the head comes into contact with the landing zone and slides on the surface until the disk comes to a rest. In such a condition, the head is "parked" in the landing zone. The landing zone is generally textured to reduce stiction ("static friction") between the head and the disk. During a disk spin-up period, once stiction is overcome, the head slides on the surface until the disk reaches sufficient rotational speed to generate an air bearing between the head and disk such that the head is "flying" above the disk. The sliding occurring during disk spin-up and spin-down periods causes disk wear which requires careful control of the interface materials (i.e., the materials forming an interface between the head and disk) and surface topographies ("textures") to ensure minimal wear over the expected life of the hard disk drive.
An alternative method of transitioning a flying head off-of and back-onto the disk is known as "rampload." This method uses a ramp which interacts with a feature ("lift tab") on a suspension that supports the head. The disk is spun-up while the suspension is supported by the ramp and the head is not in contact with the disk. Once the disk is rotating at a sufficiently high speed for generating an air bearing, the suspension and head are moved down and off the ramp until the head generates an air bearing with the disk. The suspension and head then move free of the ramp. Before the disk is spun-down, the suspension is moved onto the ramp and the head is moved away from the disk. The rampload method eliminates the wear issues associated with the CSS method.
With reference to FIGS. 1A and 1B, a prior art rampload method is shown. A portion of a head gimbal assembly is shown in FIG. 1A in which the portion includes a suspension 104, a lift tab 106 extending from the suspension, and a head 102. As shown in FIG. 1B, lift tab 106 engages with a ramp surface 110 of a ramp member 108. Ramp member 108 is part of an overall ramp which is typically coupled to a base of a disk drive. As shown in FIG. 1B, ramp member 108 is sufficiently spaced-apart vertically from a disk recording surface 113 of disk 112 and head 102 has been moved off the ramp and loaded onto disk 112. While the lift tab shown in FIGS. 1A and 1B is suitable for its intended purpose when using relatively large heads such as "Nano" sized heads (0.017 inch thick), such a lift tab poses design challenges when smaller heads are used, such as "Pico" (0.012 inch thick) and "Femto" (0.008 inch thick) sized heads. When such smaller heads are used in combination with the lift tab shown in FIGS. 1A and 1B, the distance between the lift tab and the disk recording surface decreases such that the vertical spacing between ramp member 108 and disk recording surface 113 decreases correspondingly. In such a condition, the ramp member 108 is lowered too close to disk recording surface 113 resulting in extremely tight tolerance requirements for the vertical spacing.